This invention relates to insulated gate bipolar transistors, and more specifically relates to a novel IGBT with improved ruggedness.
IGBTs are well known bipolar transistors which use a MOS-gate to control turn on and turn off. A typical IGBT structure is shown in copending application Ser. No. 08/041,136, filed Mar. 30, 1993, entitled POWER TRANSISTOR DEVICE HAVING ULTRA DEEP INCREASED CONCENTRATION REGION, which application was refiled on Sep. 30, 1994, as application Ser. No. 08/316,112, and is assigned to the assignee of the present invention. IGBTs have a higher current carrying capacity than a power MOSFET of comparable chip size and a lower forward voltage drop but are subject to failure due to the inadvertent turn on of the NPN parasitic transistor defined by the usual IGBT junction pattern. Once this transistor is activated, the parasitic thyristor turns on, causing the flow of avalanche current under the collector junction and gate region and damaging or destroying the device.
The present invention provides a novel IGBT junction pattern which has higher forward current capability and which forces avalanche to occur away from the critical active region of the IGBT.